Gender-associated diverse mitochondrial DNA molecules of the mussel Mytilus californianus

Abstract

The Pacific-rim, dioecious bivalve Mytilus californianus contains two distinct sequence types of mitochondrial (mt) DNA that are gender-limited in their occurrence. One type (F) is found in both females and males, but the second type (M) is strictly limited to males. Although F- and M-type mtDNAs occur in approximately equal proportion in testes, there is a preponderance of M-type in sperm. Segments of the COI and ND5 genes of F-type and M-type mtDNAs differ in nucleotide sequence by 21.1% and 31.6%, and in predicted amino-acid sequence by 7.9% and 27.1%, respectively. These latter observations raise hitherto unconsidered questions regarding the number of different variants of cytochrome c oxidase and NADH dehydrogenase that may occur in Mytilus non-gametic male cells.